The clinical significance of elevated blood pressure in the very old, those aged 80 and older is unclear. It s been difficult to demonstrate increased morbidity and mortality associated with elevated blood pressure in the very old. Several population-based studies have shown either no relationship or even a positive association between blood pressure and survival in the very old. We and others have shown that among the 80+ population the relationship between systolic blood pressure and mortality is more L-shaped, with highest mortality associated with systolic blood pressure of 120mm Hg or lower and lowest mortality at systolic blood pressures of 180 or higher. It has been argued that this observed L-shaped relationship is due to underlying comorbidity leading to both lower blood pressure and increased mortality. If this argument is correct, then it should be possible to identify a sub-population of healthy elderly without any comorbidity for whom the relationship of blood pressure to mortality is similar to what is found in younger populations. In this project our objective is to amine the effect of comorbidity on the relationship between blood pressure and morbidity and mortality in very old. To address these questions, we will examine the cohort of individuals at four EPESE sites (East Boston, New Haven, Iowa and Piedmont, NC) who were alive at the six year follow-up. Those 9134 subjects aged 71 years or more at 6-year follow-up point were followed for an additional 4 years. Detailed information also available regarding blood pressure, chronic medical conditions, health status, functional status, BMI, medication use and other variables. We will examine the relationship between blood pressure and adverse outcomes in the very old using Cox Proportional Hazard Analyses and Survival Analyses. Sample will be stratified based on comorbidity, functional status, blood pressure lowering medication use and blood pressure changes over time. A series of stratified analyses will be performed to examine the relationship between blood pressure and adverse outcomes, for different subsets of the older population.